diff -u b/core/includes/form.inc b/core/includes/form.inc
--- b/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -858,7 +858,8 @@
   // isset() fails in this situation.
   $value_valid = isset($element['#value']) || array_key_exists('#value', $element);
   $value_is_array = $value_valid && is_array($element['#value']);
-  $empty_value = (empty($element['#value']) && isset($element['#properties']['empty_option']));
+  // Check if the element is multiple select and no value has been selected.
+  $empty_value = (empty($element['#value']) && !empty($element['#multiple']));
   $options = '';
   foreach ($choices as $key => $choice) {
     if (is_array($choice)) {